Extern is a term that is used to refer to someone who is outside of a particular group or organization but is temporarily associated with it. If you are looking for synonyms for extern, some of the best choices include intern, guest, visitor, outsider, trainee, contractor, and consultant. These terms all refer to someone who is not permanently affiliated with a particular group or organization but is working with them in some capacity. Each of these words has its own distinct nuances and should be chosen based on context and intended meaning. By using synonyms for extern, you can express yourself more clearly and precisely in your writing and communication.